Telephone-relay.



S. G. TELEPEQSE RELAY'.

APPLIOATIUE FILED JARS, lillii w/t-[zz-eyres @Gig 9% S. G. BROWN.

TELEPHONE RELAY.

APPLICATION FILED JAN.3,1912.

1, 1 28,943. Pat-@nm Feb. 16, 1915.

D 4 SEINE? zrown i Q y Q WZXM/ S. G. BROWN.

TELEPHONE RELAY.

APPLICATION FILED JANS, 1012,

4 SHEETS'SHEBT 4 Patented Feb. 16, 1915,

SIDNEY GEORGE BROWN, OF LONDON, ENGLAN'D.

TELEPHONE-RELAY.

Specification of Letters Patent.

Patented Feb. 16, 1915.

Application tiled January 3, 1912. Serial No. 669,151.

T0 all whom it may concern:

Be it known tha I, SIDNEY GEORGE BROWN, a subject of the King of Great Britain, residing at 4 Great Winchester street, in the city and county of London, England, have invented certain new and useful Improvements Relating to Telephone-Relays, of which the following is a specification.

This invention relates to telephone relays, the chief object being to provide a compact efficient instrument of this kind, and in particular a reliable and highly sensitive form of variable resistance device for inclusion in the local circuit.

The type of variable resistance device I employ is one in which, while variations in the line'current are causing corresponding variable effects in the resistance of the device in the usual way, the current in the local circuit is utilized to maintain the variable resistance in a microphonic condition, with the result that an extremely sensitive regulation of the microphonic condition of the resistance is maintained and an efficient relay action is obtained. One practical form of variable resistance device of this kind comprises carbon granules inclosed between two contact pieces one of which is stationary and the other attached to a vibratory armature influenced by coils 'through which the line current passes and also by coils through which the local current passes. In order to obtain the highest efficiency of transmission of the vibrator-y yrgnevements of the armature from the latter to the variable resistance device it is necessary for the contact piece carried by the armature to be small in terminal area. Hence from the mechanical point of view the variable resistance device, and hence also the column of carbongranules, should be small in diameter or cross section. From the electrical point of view, however, the value ofthe maximum resistance that the carbon granules should offer has a limit, and in the case of a resistance device of small diameter or sectional area this resistance is liable to be exceeded if the mere dead weight of the granules is relied` upon. According to the present invention. therefore, the variable resistance device is of small diameter or sectional area, its excessive resistance is reduced by exerting an initial pressure upon the microphonic material contained in it, and the microphonic character of this material is automatically maintained by the effect of the local current as already described. The conductivity of the variable resistance is thereforesuch that the normal current passing through it is greater than that which it could convey by reason merely ofthe dead weight of the granules, and the regulation of this increased conductivity is effected electrically. A convenient form of the device comprises a layer or a number of separated layers of granular material, preferably carbon, the thickness of any one layer being approximately the thickness of a single granule, so that, since the layer is only one granule deep, the defect commonly existing in granular contact devices due t-o packing of the granules is avoided. The most effective parts of granules are their points and edges, and when a considerable mass of granules is used the particles tend to take up positions alongside one another, and to wedge into one another, whereas if a single layer. or a number of separated layers one ranule deep is em-` ployed, the full effect o the end-on positions of the granules, or in other words the maximum effect of their points and edges, is obtained. Although metallic particles may be used as the granular material, I find fine carbon grains to yield excellent results. The contact pieces between which the one or more thin layers of granular material are situated may comprise carbon or metal stops, one being normally stationary, although manuallv adjustable for the` purpose of setting the instrument, the other being mounted on a vibratory reed serving as the armature of the usual polarized electromagnet. In order to keep the granules in position laterally, a short sleeve, preferably of glass and having a limited axial freedom of movement, may be employed.

It is found advantageous in practice for the movable contact and hence also the axis of the whole resistance device to be eccentric with respect to the axis of the magnetic field that influences the armature, the eccentricity or displacement being toward the fixed end of the armature.

In addition to the electromagnct windings through which the line currents pass, and the electromagnet windings through which the local current passes for maintaining the microphonic condition of the variable resistance device, the electromagnet mav also have wound upon it counteracting windings that are brought into action only if the attracting force exerted upon the armature bv the other windings becomes excessive, the effect of these counteracting windings then being to neutralize this attracting force.

In order that the invention may be clearly understood and readily carried into effect, I will now describe the same more fully w-ith reference to the accompanying drawings, in which Figure' l is a diagrammatic plan of my improved relay and its connections to the line and to a local circuit. Fig. 2 is a diagram of electrical connections in the local circuit including the connections for the counteracting coils. Fig. 3 is a side elevation, Fig. 4 a plan, and Fig. 5 a sectional elevation of the complete instrument to full size. Fig. 6 is an enlarged detail longitudinal section of one form of the variable resistance device, and Fig. 7 is a modified form of this device. Fig. 8 is a much enlarged cross section of a disk that may be employed in the yconstruction of a further modified form of variable resistance device, as hereinafter described. Fig. 9 is a Ifront elevation and Fig. 10 a side elevation, with certain parts removed, of a modified form of the relay, in which two variable resistance devices areused. Fig. 11 is a diagram of connections for the device shown in Figs. 9 and 10. Figs. 12, 13 and 14 illustrate a further modified construction of relay hereinafter referred to.

A A are the line wires leading to and from the line current windings A', and B B are the wires leading to and from the local current windings B.

C is the polarized electromagnet. The windings B are wound around upright cores C', which are secured to the ends of the electromagnet C; the counteracting windings hereinbefore referred to, and shown in Fig. 2 by the reference letters B", are also wound upon the cores C. These cores may be inclosed in copper sheathing c in order that eddy currents set up in the sheathing may tend to neutralize the self induction of the superposed windings.

The windings A are wound upon laminated pole pieces C2, secured horizontally by brass screws to the upper ends of the cores C. The free ends of the pole pieces C2 are close together and are situated behind the armature D.

E is the variable resistance device, this being` included in the local circuit which includes Valso the windings B', switch B2, source of electric current B3, detector B", and transformer winding B5. The other transforming winding B6 is included in the actual circuit of the telephone receiver B7. Obviously the telephone might be connected directly in the local circuit, and is in fact so shown in Fig. 2.

\ticu1ar construction of variable The armature D carries the contact piece D of the pair of contact pieces D', E, (Fig. 6) of the variable resistance device E, which may conveniently be .0S to .1 of an inch in diameter. rIhe contact piece E forms part of a block E2 (Fig. 4) which is adjustably mounted in a bearing E3 carried by an insulating bed plate E4. This insulating bed plate is capable of' longitudinal adjustment by means of the thumb screw E5 ardu/nd which is coiled a stili' spring E6 (Figs. 4 and 5). Between the contact pieces D', E', the one or more thin layers of microphonic material are inclosed. rl`he parresistance device shown in Figs. 1-5, and'in detail in Fig. (i, comprises in addition to the contact pieces D', E', three thin layers of carbon grains separated by thin disks E7 of carbon or metal faced with carbon. Each thin layer is only one grain deep approximately. The grains are inclosed by a sleeve Es of practically inextensible material in order to prevent lateral expansion and thereby insure an efficient axial transmission of variations in pressure. Glass is found satisfactory for this'purpose and has the additional advantage of allowing -of examination of the device from the outside. The longitudinal axis of the device as a whole is displaced relatively to the axes of the electromagnet pole pieces C2 the displacement being toward the fixed end of the armature D. It is found in practice that by locating the device E in this way, the vibrations of the armature are transmitted to the device more efficiently than if the latter were located actually at the free end of the said armature or in the plane of the axes of the electromagnet pole pieces. The armature itself may take the form of a steel reed the free end of which may be of steel or of soft iron. An intermediate part of the reed is preferably cut away as at D2 in order to impart the requisite resiliency to it. The said reed is held down upon a rounded bridge piece D3 by two screws D4, one on each side of the bridge piece.

In the modified form of resistance device shown in Fig. 7, the disks E7 extend outwardly beyond the layers and serve as radiating flanges to more quickly dissipate the heat produced in the device when in operation. In this case the sleeve is substituted by mere rings of any suitable somewhat elas. tic material. The disks E7 instead of having plain surfaces as shown, might have surfaces specially roughened in order to interlock to some extent with the grains and more effectually hold them in place; th roughening of the said surfaces may be done syanlnetrically, for instance by ruling grooves E9 upon them as shown in Fig. 8, the grooves on one surface being ruled in a transverse direction with respect to those on the other surface.

ladgusted to put tramas If two or more suchdisks are piled together,

with their grooves crossing one another, a large number of contact points will be obtained, thus producing the equivalent of a layervof grains, with, however, the advantage that the points of contact Would not be liable to change in position and would be symmetrically arranged relatively to one another.

The manner in which the instrument Works will be readily understood. The screw is a degree of pressure upon the variable resistance device such that, when the switch is closed, the attracting force of the local circuit windin s will move the electromagnet armature sufhciently to reduce the pressure enough to establish the microphonic condition of the device. Variations in the strength of the current tr* versing the line windings will then cause variations in the resistance of the device but such variations by reason of the copper sheathing on the upright cores of the magnet do not affect the local regulation, with the result that a very sensitive regulation is maintained, and a sensitive relay action obtained.

Referring now to Fig. 2, it will be seen that the reed D is provided at its free end with a tongue D5 reaching between two stops DG and DT. Under normal conditions of working the amplitude of vibration of the reed is not suflicient to produce contact between the tongue D5 and the stops D, D7, but when the attraction of the electromagnet pole pieces C2 contact takes place; the effect is to complete the circuit of one or other of the counteracting windings B", BX, which, together with a resistance D8, are included in circuits adapted to derive current from the battery B3 as clearly shown in the figure. The windings BX, BX. are wound co-axially with the windings B, B. and are arranged to reduce or increase respectively the strength of the magnetic circuit, thus preventing the reed D from becoming excessively attracted, or repelled, by reason of any excessive disturbing relay currents or currents arising from outside sources and passing through the instruinent.

In the modified construction of relayv shown in Figs. 9 and 10, and diagrammatically in Fig. ll, it is seen that there are two variable resistance devices ICO and IC", arranged one upon each side of a common armature D A 9, AO, are the line current windings, Il", BO, the local current windings, and F". FO. are tlg counteracting windings. which may not however be required. The armature l),X is norn'lally kept in a midposition by the equal attraction of the two :similar cores or pole pieces lll", which are capalile of ad iustinent by means of the thumb screws FP. The requisite pressure exerted upon the carbon granules in the resistance becomes excessive thisv the granules is not in this case sullicient to impair their microphonic property, which property is, in the constructions above described, restored by the partial relief of the pressure brought about by the local Windings; in the present construction the pressure applied is only sufficient to put the granules into their most sensitive microphonic condition; any disturbance, however, tending to move the armature Dx excessively and thereby upset the microphonic condition is checked by the action of the local current windings, since an excessive drop or rise in the conductivity of the granules causes a corresponding decrease or increase in the magnetic influence of these windings. Briefly stated, the local current windings, although not establishin the microphonic condition of the devices LO E", serve to maintain them in that condition.

In a further modified form of the instrument shown in Figs. 12, 13 and 14, the-armature DO, instead of being held down, by screws, upon a rounded bridge piece as in Figs. 2, 3 and 5, and being thereby rendered adjustable in position relatively to the freeends of the electromagnet pole pieces C2, is rigidly and permanently fixed to the framework of the instrument, and the adjustment of the small space between the armature and the pole pieces is effected by moving the latter. For this purpose the upright cores C of the polarized magnet are severed as shown by the dotted lines Cx. so that the portions attached to the pole pieces C2, together with the said pole pieces and the windings A thereon, can be bodily advanced or retracted relatively to the armature DO. In the drawings these parts are shown mounted upon a bed plate Cn capable of being traversed by a screw. In order that the magnetic circuit of the magnet may not be detrimentally afffected` the C-shaped magnet C and the lower portions of' the upright cores (.f may be mounted upon upwardly thrusting springs C adapted to keep the severed portions of the cores in firm contact with one another.

What I claim and desire to secure b v Let.- ters latent ot' the United States is:u

l. A telephone relay, comprising a mag net, line current windings thereon, a vibra toiv armature associated with said nragne, a granular microphone of the order of .l of an inch in diameter. one contact piece of the microphone being attached to the aforesaid armature, means for initially applying pressure upon the microphonic material, and

electrical means for relieving the pressure and thereby establishing and maintaining the microphonic condition of the microphone.

2. A telephone relay, comprising a magnet, line current windings thereon, a vibratory armature associated with said magnet, a granular microphone of the order of .1 of an inch in diameter, one contact piece of the microphone being attached to the aforesaid armature, means for initially applying pressure upon the microphonic material, and windings on the magnet connected in series with the microphone. y

3. A telephone relay, comprising a magnet, line current windings thereon, a vibratory armature associated with said magnet, a granular microphone of the order of .1 of an inch in diameter, one contact piece of the microphone being attached to the aforesaid armature, means for initially applying pressure upon the microphonic material, windings on the magnet connected in series with the microphone, and means whereby any excessive magnetic influence upon the armature automatically throws into action a counteracting influence.'

4. A telephone relay, comprising a magnet, line current windings thereon, a vibratory armature associated with said magnet, a granular microphone of the order of .1 of an inch in diameter, one contact piece of the microphone being attached to the aforesaid armature, means for initially applying pressure upon the microphonic material, windings on the magnet connected in series with the microphone, windings on the magnet wound counteractingly with respect to the line windings, and means arranged for cooperation with the armature to complete the circuit of the counteracting windings when the armature tends to vibrate excessively.

5. A telephone relay, comprising a magnet, line current windings thereon, a vibratory armature associated with said magnet, a granular microphone of the order of .1 of an inch in diameter, one contact piece of the microphone being attached to the aforesaid armature, means for initially applying pressure upon the microphonic material, windings on the magnet connectedin series with the microphone, windings on the magnet wound counteractingly with respect to the line windings, stops connected electrically with the counteracting windings, and an extension on the vibratory armature for cooperation with said stops.

6. A telephone relay comprising a polarized electromagnet, line current windings thereon, a metal reed serving as armature to said electromagnet, a granular carbon microphone of the order of .1 of an inch in diameter, one Contact piece of the microphone being attached to the aforesaid armature, means for adjusting the other contact piece to apply pressure to the granules,

windings on the electromagnet connected in series with the microphone, and means for limting the vibratory movements of the ree 7. A telephone relay, comprising a polarized electromagnet, electromagnet windings forming part of the line circuit, a resilient reed serving as armature to said electromagnet, a contact piece secured to the aforesaid reed, an oppositely stationary contact piece, separated layers of granular material located between the contact pieces, each layerbeing of the order of .1 of an inch in diameter and approximately one granule thickfmeans inclosing the granules laterally, means for adjusting the normally stationary contact piece, and electromagnet windings forming part of a local circuit yincluding the aforesaid contact pieces and layers of granular material.

8.r A telephone relay, comprising a polarized electromagnet, electromagnet windings forming part of the line circuit, a resilient reed serving as armature to said electromagnet, a contact piece secured to the aforesaid reed, an oppositely situated normally stationary contact piece, separated layers of carbon granules located between the contact pieces, each layer being of the order of .1 of an inch in diameter and approximately one granule thick, thin conducting disks separating the layers, an axially movable glass sleeve inclosing the granules and disks laterally, means for adjusting the normally stationary contact piece, and electromagnet windings forming part of a local circuit 1ncluding the aforesaid contact pieces and layers of granular material.

. 9.*A telephone relay, comprising a polarized electromagnet, an clectromagnet armature, electromagnet windings forming part of the line circuit, electromagnet windings forming part of the local circuit, a granular carbon microphone having a contact piece movable with the aforesaid electromagnet armature and a granule chamber of the order of .1 of an inch in diameter, electromagnet windings acting to counteract the effect, upon the armature, of the other windings, means cooperating with the armature for controlling the circuit of the counteracting windings, and means for exerting an initial pressure upon the granules.

10. A telephone relay comprising a horizontal polarized electromagnet, upright cores thereon, local current windings upon the cores, converging pole pieces secured horizontally to the cores, line current windings upon the pole pieces, a resilient reed serving as electromagnet armature, a granular carbon microphone having a contact piece movable with the reed and a granule chamber of the order of .1 of an inch in diameter, and means for exerting an initial pressure upon the granules.

situated normally 11. A telephone relay, comprising a horigranule thick, thin carbon disks separating l zontal polarized electromagnet, upright the said layers, an axially movable glass cores thereon, local current windings upon sleeve inclosing the granules and disks latthe cores, converging pole pieces secured erally, and means for adjusting the norhorizontally to the cores, line current windmally stationary Contact piece for exerting ings upon the pole pieces, a resilient reed an initial pressure upon the granules. serving as electromagnet armature, a granu- 13. A telephone relay, comprising a polarlar carbon microphone having a contact ized electromagnet, upright cores thereon, piece movable with the reed and a granule copper sheathing around the cores, local chamber of the order of .1 of an inch in current windings upon the sheathing, lamidiameter, means 'for exerting an initial nated pole pieces secured horizontally to pressure upon the granules, and means for the cores, line current windings upon the adjusting the air gap between the above pole pieces, an electromagnet armature, a mentioned pole pieces and the reed. granular carbon microphone included in the 12. A telephone relay comprising a polarlocal circuit and having a granule chamber ized electromagnet, upright cores thereon, of the order of .1 of an inch in diameter, one local current windings upon the cores, concontact piece of the device being fixed to the verging pole pieces secured horizontally to aforesaid electromagnet armature, and said cores, line current windings upon the means for exerting an initial pressure upon pole pieces, an electromagnet armature, a the granules.

contact piece secured to the aforesaid arma- In testimony whereof I aflix my signature ture, an oppositely situated normally sta- 1n presence of two witnesses.

tionary contact piece, separated layers of 4 SIDNEY GEORGE BROWN. carbon granules located between the contact Witnesses:

pieces, each layer being of the order of .1 of T. SELBY WARDLE,

an inch in diameter and approximately one WALTER J. SKERTEN. 

